This article paraphrases the materials strategy of October 2026. It gives the thinking; the numbers will come as the tests do.
The material has two jobs that pull against each other
A floating brick must be light enough to give useful buoyancy and strong enough to carry the forces that pass between bricks when a platform flexes in a swell. Fibre composites did the second job well. They were never going to do the first on their own, and they brought the problem of water with them. The strategy that emerged through 2026 gives each job to a different part of the brick.
A light core and a dense shell, with fibre throughout
The core is a mineral foam: a low-density mineral composite that supplies most of the buoyancy. The lighter the core, the more the structure can carry.
The shell is a denser mineral layer around the core, thickest where bricks grip one another. It protects the core, gives a hard surface at the joints and carries contact loads. The outer surface of a whole structure is coated independently of the bricks, the way a ship's hull is, with a cladding that can be replaced every few years.
The fibre remains an important part of the composite. The fibres mineralize into an internal scaffolding which gives the brick strength and flexibility. Flax, hemp and kelp all work; the choice is about what grows nearby.
Why mineral
Mineral binders cure without the clinker that gives Portland cement its carbon footprint, and seawater does not eat them the way it eats reinforced concrete. Mineralizing agents mixed with the fibre crystallize as water slowly permeates, so the brick becomes a self-healing, stone-like matrix and gets stronger with age. The fibre inside is sequestered carbon: each brick stores more than its own weight in CO2. The question we keep asking is how inexpensive and how scalable we can get while holding a hard line on sustainability.
What the next round tests
The interlocking brick shape is finalized. The next round of work tests the combination of foam core, protective shell, waterproofing, curing and small-batch production at full size, in marine conditions;
- Density, dry and conditioned, and how much it varies from batch to batch.
- Water uptake under immersion, pressure and wet-dry cycling.
- Shrinkage, fibre toughness and the bond between core and shell through curing and ageing.
- Placing and demoulding one finished brick per cycle from a two-part mould.
The kelp composite and the flax and hemp work are what taught us about fibre, binders, moisture and supply. The mineral foam is where that learning has arrived.